Class-A amplifier circuit having output voltage varied according to input voltage

Abstract

A class-A amplifier circuit having output voltage varied according to input voltage includes a class-A amplifier, a voltage pull-up switch level circuit, an output voltage of the class-A amplifier, a voltage pull-up switch circuit, a voltage pull-down switch level circuit, a voltage pull-down circuit, a voltage pull-down switch circuit, and a bias circuit. The circuit utilizes the voltage pull-up and the voltage pull-down circuits to enable an output voltage of the class-A amplifier to rapidly and precisely change as an input voltage changes. Moreover, the circuit utilizes the voltage pull-up and the voltage pull-down switch circuits to prevent an overshooting from occurring.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a class-A amplifier and, more particularly, to a class-A amplifier circuit having output voltage capable of being rapidly and precisely varied as an input voltage changes.2. Description of Related ArtOutput voltages of conventional CMOS (complementary metal oxide semiconductor) class-A and class-AB amplifiers are shown in FIGS. 1 and 2. In FIG. 1, input voltage is boosted from a low level (e.g., VSS+2V≈2V) to a high level (e.g., VDD≈10V). On the contrary, in FIG. 1, input voltage is lowered from a high level (e.g., VDD≈10V) to a low level (e.g., VSS+2V≈2V). It is seen that there is no overshooting in the output voltage of the class-A amplifier in either figure. However, a relatively long period of time is required for either rising the output voltage of the class-A amplifier from the low level to the high level or lowering the same from the high level to the low level. This can limit an operating fr...

AI Technical Summary

Benefits of technology

An object of the present invention is to provide a class-A amplifier circuit having voltage pull-up and voltage pull-down capabilities so that its output voltage is capable of being rapid and precisely changed as an input voltage changes.

Another object of the present invention is to provide a class-A amplifier circuit having voltage pull-up and voltage pull-down switch capabilities so as to increase a voltage pull-up or pull-down in order to prevent an overshooting from occurring.

Problems solved by technology

However, a relatively long period of time is required for either rising the output voltage of the class-A amplifier from the low level to the high level or lowering the same from the high level to the low level.

This can limit an operating frequency of the class-A amplifier.

Unfortunately, the output voltage of the class-AB amplifier tends to overshoot, resulting in a generation of noise in the device.

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